Constant delivery pump system



Nov. 7, 1967 A. D'AMATO 3,

CONSTANT DELIVERY PUMP SYSTEM Filed Jan. 1:5, 1 966 5 Sheets-Sheet 1 MICHAEL A. D'AMATO ATTORNEY INVENT OR 7 Nov. 7, 1967 M. A. DAMATO CONSTANT DELIVERY PUMP SYSTEM Filed Jan. 13, 1966 m m W g ng;

INVENTOR MKIHAEL A. D'AMATO A RNEY United States Patent 3,350,881 CONSTANT DELIVERY PUMP SYSTEM Michael A. DAmato, West Des Moines, Iowa, assignor to Delavan Manufacturing Company, West Des Moines, Iowa, a corporation of Iowa Filed Jan. 13, 1966, Ser. No. 520,336 Claims. (Cl. 60-52) ABSTRACT OF THE DISCLOSURE The system comprises a variable displacement pump having a casing, a central shaft rotatable in the casing, a cylinder block rotating with the shaft, and a plurality of pistons in the cylinder block. Ends of the pistons engage a swash plate which is tipped between a maximum angular position for maximum piston stroke and, hence, maximum pump delivery and a zero angular position for no piston stroke and, hence, Zero pump delivery by means of a pair of opposing plungers, one of larger diameter than the other. The smaller plunger is constantly biased by fluid from the high pressure side of the pump tending to tip the swash plate towards zero angle. The larger plunger is constantly biased to tip the swash plate towards maximum angle by means of a compression spring and sometimes by pressure fluid from the high pressure side of the pump, which pressure fluid is controlled by a differential valve. Connected in a delivery line between the high pressure side of the pump and a load is a variable orifice. Pressure fluid tapped off from the delivery line upstream of the orifice biases the differential valve in one direction in which it tends to isolate the larger plunger from pressure fluid from the pump and, hence, reduce pump delivery. Pressure fluid from the delivery line downstream of the orifice actuates the differential valve in the opposite direction in which it tends to expose the larger plunger to pressure fluid from the pump. A spring also biases the differential valve in the direction in which it tends to expose the larger plunger to the pressure fluid from the pump.

This invention relates to a constant delivery pump system utilizing a variable delivery fluid pump and, moreover, a system for maintaining constant delivery to a work load despite variations in the work load or variations in pump speed.

The primary object of the invention is to provide a system utilizing a variable delivery fluid pump, an orifice in the delivery line for establishing a predetermined pressure drop between the pump output and a work load, and a pressure responsive differential pump delivery control mechanism which senses relative pressures between the pump output and the orifice, on the one hand and, on the other hand, between the orifice and the work load, and which controls the delivery of the pump in such manner as to maintain the pump output pressure, as seen on the upstream or pump side of the orifice, at a predetermined number of pounds per square inch above the pressure on the downstream or work load side of the orifice. Thus, no matter what the pump speed or work load demand may be, the orifice and the differential valve permit only a predetermined maximum of pumped fluid to flow to the work load, and the delivery of the pump is so maintained as to deliver sufficient pumped fluid to the orifice as to maintain the flow of pumped fluid through the orifice at that predetermined rate established by the orifice.

These and other objects will be apparent from the following specification and drawings, in which:

FIG. 1 is a cross section through a typical variable delivery pump suitable for use in the system and a diagram of the associated system;

FIG. 2A is an enlarged fragmentary cross section show- 3,350,881 Patented Nov. 7, 1967 ing the feedback sensor piston and pump control valve in position to increase pump delivery;

FIG. 2B is a view similar to FIG. 2A, but showing the feedback sensor piston and pump control valve in position to decrease pump delivery;

FIG. 3 is a fragmentary cross section of the pump control valve offset from the cross section of FIG. 2A;

FIG. 4 is a broken-off elevation of the output end of the pump, showing the variable orifice valve and connections thereof with the pump;

FIG. 5 is a cross-section through the variable orifice valve, with its handle removed, along the line 55 of FIG. 4;

FIG. 6A is a cross-section through the variable orifice valve along the line 6A of FIG. 5 showing the variable orifice valve open; and,

FIG. 6B is a fragment of FIG. 6A showing the variable orifice valve closed.

Referring first to FIG. 1 the variable displacement pump 2 shown therein is basically the same as that shown in my prior US. Patent No. 3,221,660 entitled Automatic Control for Variable Displacement Pump. A brief resume of pump 2 and its mode of operation is as follows:

Pump 2 has a casing 6 in which is rotatably mounted a drive shaft 3 which is driven by a prime mover (not shown). Keyed to the drive shaft and rotating therewith is a barrel 10 having therein a plurality of axially extending cylinders 12. In the cylinders are pistons 14 whose knuckle-ends 16 are forced by springs 18- ag-ainst a pivoted swash plate 20 so that the pistons 14 reciprocate when the drive shaft 8 rotates. The ends of cylinders 12 pass over somewhat kidney-shape ports (not shown) in a port plate 22 so that when the pistons move to the left as seen in FIG. 1, fluid is forced out through an output conduit 24, a portion of which in the pump casing 6 is diagrammatically indicated by dash lines, and when the pistons move to the right, fluid is drawn in through an inlet passage 26, also diagrammatically indicated in part by dash lines. One control plunger 28 is constantly forced against one side of swash plate 20 by pressure fluid in its cylinder 30 derived via a duct 32 from output passage 24. Another control plunger 34, slightly larger in diameter than plunger 28, is biased against the other side of swash plate 20 by a spring 36. Under certain conditions, depending upon the position of control valve 4, the cylinder 38 behind control plunger 34 is supplied with pressure fluid from output conduit 24 via duct 44 and valve 4, whereupon the force exerted by plunger 34 against swash plate 20 overcomes that exerted by control plunger 28 and swash plate 20 is tilted about its pivot (not shown) to the position of FIG. 1 wherein maximum stroke length of pistons 14 and hence maximum delivery of the pump is provided. Under other conditions, control valve 4 cuts off cylinder 38 from communication with outlet conduit 24 and ultimately establishes communications via an exhaust line 41 with a fluid reservoir 42 so that low fluid pressure prevails in cylinder 38 and the force exerted by control plunger 28 overcomes the force of spring 36 and swash plate 20 is tilted towards or to a 0 angle and the stroke of pistons 14 is correspondingly reduced. In actual practice, exhaust line 41 extends through pump casing 6 to the inner cavity of the pump which, in turn, is externally ported directly to reservoir 42. In the condition of valve 4 shown in FIGS. 1 and 2B, the force of plunger 28 on swash plate 20 is about to overcome that exerted by plunger 34 so that swash plate 20 will be tipped towards a neutral position.

The invention resides in the system, which includes an orifice 44 in output delivery conduit 24 which leads to a load 46 which ordinarily would include a fluid motor, a return line 48 from the load to fluid reservoir 42 and,

in accordance with good engineering practice, a pressure relief valve 50 connected between that portion 24:: of output conduit 24 which lies between orifice 44 and load 46, and return line 48, a feedback line 52 which leads from portion 24a of output conduit 24, i.e., downstream of orifice 44, and the feedback sensor 54 and valve 4 described hereinafter.

Referring particularly to FIGS. 2A, 2B and FIG. 3, valve 4 is of the spool type, consisting of a reduced neck 56 connecting two cylindrical enlargements 58 and 60, and a stop projection 62 on the outer end of enlargement 60. Valve 4 slides in the cylindrical bore 64 of a shell 66, which plugs into a cylindrical recess 68 in pump casing 4 behind cylinder 38 and which is sealed by rings 70. The exterior of shell 66 and cylindrical recess 68 are so stepped as to define between them an annular chamber 72 into which duct 40 from the output conduit 24, i.e., the high-pressure side of pump 2 leads, and a port 74 leads inwardly from annular chamber 66 to the cylindrical bore 64 of shell 66. Also, a branch 76 connects port 74 with the chamber 78 defined between the closed end 80 of shell 66 and the cylindrical enlargement 60 of valve 4 so that chamber 78 is always connected with the high pressure side of the pump, and a chamber 82 lying between cylindrical enlargements 58, 60 and between neck 56 and the wall of cylindrical bore 64 is connected with the high pressure side of the pump when valve 4 is forward in the FIG. 2A position. Two channels 84, 86 lead from cylinder 38 through shell 66 into the rear of chamber 82 so that when valve 4 is forward in the FIG. 2A position cylinder 38 is connected to the high pressure side of the pump via duct 40, chamber 72, port 74, chamber 82 and channels 84, 86. However, when valve 4 is in its rearward FIG. 2B position, cylinder 38 is connected to exhaust line 41 via channels 84, 86 chamber 82, the then exposed rear edge of hole 88, a chamber 90 surrounded by a cylindrical skirt 92 on the rear end of shell 66, ports 94 through skirt 92 and exhaust line 41.

Axially slidable through a cylindrical bore 98 in a fitting 100 threadedly engaged as at 102 in the end of cylindrical bore 64 is the feedback sensor piston 54. Piston 54 is slidably sealed in bore 98 by 0 rings 104 and its forward end abuts the rear enlargement 58 on valve 4. Piston 54 is biased forwardly against valve 4 by means of an expansion spring 106 which engages between an end wall 108 in fitting 100 and a washer 110 held on piston 54 by a snap collar 112. A stop sleeve 114 limits the rearward movement of piston 54. The force exerted by spring 106 on piston 54 is equal to 100 p.s.i. in chamber 78 against the forward end of valve 4. The space 116 at the rear end of piston is connected to feedback line 52 by means of a suitable threaded coupling 118 (FIG. 4).

Referring particularly to FIGS. 4, 5, 6A and 6B, orifice 44 is formed in a variable orifice valve 120 whose casing 122 may, as in the present example, be mounted directly on pump casing 6 by suitable bolts 124. Valve 120 has an inlet 24' connecting with the pump output conduit 24 and an outlet 24a connected with that portion 24a of the output conduit 24 which lies downstream of orifice 44, and a feedback passage 52 connecting with feedback line 52. The cross-section of orifice 44 and hence the fiow therethrough and pressure drop thereacross may be adjusted as follows:

Rotatably mounted in a crossbore 126 is a hollowended shaft 128 whose inner end has an internally threaded portion 130. A hollow enlargement 132 within the hollow shaft 128 terminates in an inclined shoulder 134 which extends inwardly to internally threaded portion 130, and a 180 slot 136 is cut through the wall of shaft 126 near the inner end of enlargement 132. Engaging in hollow enlargement 132 is a plug 138 which has an externally threaded reduced inner end 140 threadedly engaging the internally threaded portion 130' of shaft 128. It will be seen from FIG. that the plug 138 may be screwed inwardly and outwardly with respect to hollow shaft 128, and that an inclined shoulder 142 on plug 128 is disposed in the region of the 180 slot 136 in the hollow-ended shaft 128. Inward or outward adjustment of plug 138 in hollow-ended shaft 128 varies the effective width of slot 136 and, hence, the cross-section of orifice 44. Once orifice 44 is properly adjusted as to size, plug 138 is locked into place by inserting a threaded tapered lock plug 144 into its split internally threaded open end. Opening (FIG. 6A) and closing (FIG. 6B) of the variable orifice valve is effected by swinging of a handle 146 which is attached onto the outer end of shaft 128.

The mode of operation is as follows: If pump 2 were started with variable orifice valve 120 closed so that the pressure in output delivery line 24a downstream of valve 120 is zero, the pump would develop enough pressure in output delivery line 24 upstream of valve 120 until the force in chamber 78 on the inner end of valve 4 would overcome the force exerted by spring 106, whereupon valve 4 would shift to the left, as seen in FIG. 2B, cylinder 38 would be vented via exhaust line 41, whereupon plunger 28 would shift swash plate 20 towards a neutral position enough to maintain p.s.i. pressure in output delivery line 24. Let it be next assumed that variable orifice valve 120, having been adjusted to permit a flow of 5 g.p.m. therethrough and to provide a pressure drop of 100 p.s.i. thereacross, is opened. Pump 2 will then deliver enough oil to maintain the 100 p.s.i. against the orifice. When this 100 p.s.i. tends to increase, valve 4 moves to the left against the force of spring 106 and delivery is reduced to maintain this fixed pressure differential. Now, let it be assumed that the work load requires 1000 p.s.i. This pressure is sensed via feedback line 52. Feedback sensor piston 54 then applies against valve 4 the fluid force of 1000 p.s.i., plus the spring force equal to 100 p.s.i., thus making a total force equal to 1100 p.s.i. against the outer end of valve 4 so as to move valve 4 to its FIG. 2A position. Plunger 34 will thereupon force swash plate 20 towards maximum delivery angle until the pump develops 1100 p.s.i. in output delivery line 24, and when the pump output pressure tends to rise above 1100 p.s.i., valve 4 will be shifted to the left sufficiently to maintain the 1100 p.s.i. in output delivery line 24 upstream of orifice 44.

In typical operation, let it be assumed that load 46 is a hydraulic motor driving a conveyor which is intended to run at one speed. Plug 138 in variable orifice valve is adjusted outwardly so as to provide full opening of variable orifice 44 and, with valve 120 open, pump 2 is started to produce the lowest flow (lowest speed) that will operate the motor at the highest speed of intended use. Plug 138 is then adjusted inwardly to reduce the size of orifice 44 until a slight reduction in the work load speed is detected. The 100 p.s.i. pressure drop has now been established and work load speed can be varied at this point to the closed position of the orifice. After the pressure drop has been established, the prime mover for pump 2 is adjusted to the slowest operating speed, and the orifice is adjusted to give the desired work load speed, and lock plug 144 is inserted. Assuming the orifice has been adjusted, for example, to provide 5 g.p.m. flow therethrough, this flow remains constant, no matter what the pump speed or work load demand, because of orifice 44 and the differential forces acting upon valve 4. Ordinarily, valve 4 will float back and forth between its FIG. 2A and 2B positions.

The invention is not limited to the details shown and described herein, but is intended to cover substitutions, modifications and equivalents within the scope of the following claims:

I claim:

1. In combination, a variable delivery pump adapted to be connected through an output delivery line to a work load and adapted to receive fluid from a reservoir, orifice means in the output delivery line establishing a pressure drop therein, said pump being of the type having control plunger means responsive to fluid pressure in a cylinder therefor of greater than a predetermined force for adjusting said delivery in a direction tending to increase output of said pump and being responsive to fluid pressure in said cylinder of less than said predetermined force for moving said control plunger means in a direction tending to decrease delivery of said pump, casing, conduit and control valve means, said control valve means being movable between first and second positions respectively for alternatively connecting said cylinder to the output delivery line upstream of said orifice means and for venting said cylinder to said reservoir, said control valve means including first piston surface means and a first chamber therefor, said first piston surface means facing in a direction such that pressure of fluid in said first chamber tends to move said control valve towards said second position, conduit means establishing a permanent fluid connection between said output delivery line upstream of said orifice means and said first chamber, second piston surface means and a second chamber therefor, said second piston surface mean-s facing in a direction such that pressure of fluid in said second chamber tends to move said control valve means towards said first position, and conduit means establishing a fluid connection between said second chamber and said output delivery line downstream of said orifice means.

2. The combination claimed in claim 1, and a spring engaging between said Casing and control valve means and establishing a permanent bias thereon tending to move the same towards said first position.

3. The combination claimed in claim 2, the second piston surface means being substantially equal in working surface area to the working surface area of the first piston surface means.

4. In the combination claimed in claim 1, a spring engaging between said casing and said control valve means and establishing a permanent bias thereon tending to move the same towards said first position, said second piston surface means being substantially equal in working surface area to the Working surface area of said first first piston surface means, said orifice means being a variable orifice control valve.

5. The combination claimed in claim 1, said orifice means being a variable orifice control valve.

References Cited UNITED STATES PATENTS 2,238,061 4/1941 Kendrick 60-52 3,221,660 12/1965 DAmato 103-162 X EDGAR W. GEOGHEGAN, Primary Examiner. 

1. IN COMBINATION, A VARIABLE DELIVERY PUMP ADAPTED TO BE CONNECTED THROUGH AN OUTPUT DELIVERY LINE TO A WORK LOAD AND ADAPTED TO RECEIVE FLUID FROM A RESERVOIR, ORIFICE MEANS IN THE OUTPUT DELIVERY LINE ESTABLISHING A PRESSURE DROP THEREIN, SAID PUMP BEING OF THE TYPE HAVING CONTROL PLUNGER MEANS RESPONSIVE TO FLUID PRESSURE IN A CYLINDER THEREFOR OF GREATER THAN A PREDETERMINED FORCE FOR ADJUSTING SAID DELIVERY IN A DIRECTION TENDING TO INCREASE OUTPUT OF SAID PUMP AND BEING RESPONSIVE TO FLUID PRESSURE IN SAID CYLINDER OF LESS THAN SAID PREDETERMINED FORCE FOR MOVING SAID CONTROL PLUNGER MEANS IN A DIRECTION TENDING TO DECREASE DELIVERY OF SAID PUMP, CASING, CONDUIT AND CONTROL VALVE MEANS, SAID CONTROL VALVE MEANS BEING MOVABLE BETWEEN FIRST AND SECOND POSITIONS RESPECTIVELY FOR ALTERNATIVELY CONNECTING SAID CYLINDER TO THE OUTPUT DELIVERY LINE UPSTREAM OF SAID ORIFICE MEANS AND FOR VENTING SAID CYLINDER TO SAID RESERVOIR, SAID CONTROL VALVE MEANS INCLUDING FIRST PISTON SURFACE MEANS AND A FIRST CHAMBER THEREFOR, SAID FIRST PISTON SURFACE MEANS FACING IN A DIRECTION SUCH THAT PRESSURE OF FLUID IN SAID FIRST CHAMBER TENDS TO MOVE SAID CONTROL VALVE TOWARDS SAID SECOND POSITION, CONDUIT MEANS ESTABLISHING A PERMANENT FLUID CONNECTION BETWEEN SAID OUTPUT DELIVERY LINE UPSTREAM OF SAID ORIFICE MEANS AND SAID FIRST CHAMBER, SECOND PISTON SURFACE MEANS AND A SECOND CHAMBER THEREFOR, SAID SECOND PISTON SURFACE MEANS FACING IN A DIRECTION SUCH THAT PRESSURE OF FLUID IN SAID SECOND CHAMBER TENDS TO MOVE SAID CONTROL VALVE MEANS TOWARDS SAID FIRST POSITION, AND CONDUIT MEANS ESTABLISHING A FLUID CONNECTION BETWEEN SAID SECOND CHAMBER AND SAID OUTPUT DELIVERY LINE DOWNSTREAM OF SAID ORIFICE MEANS. 